A basic Async Sequence in Swift for HTML Parsing

.swift

import SwiftUI

// today coding: async sequence in Swift

struct URLSequence: AsyncSequence {
    typealias AsyncIterator = URLIterator
    typealias Element = Data
    
    let urls: [URL]
    
    func makeAsyncIterator() -> URLIterator {
        URLIterator(urls: urls)
    }
}

struct URLIterator: AsyncIteratorProtocol {
    typealias Element = Data
    
    let urls: [URL]
    
    fileprivate var index: Int = 0
    private let urlSession = URLSession.shared
    
    mutating func next() async throws -> Data? {
        guard urls.count - 1 >= index,
              case let url = urls[index]
        else { return nil }
        
        defer {
            index+=1
        }
        
        // main here
        let (data, _) = try await urlSession.data(from: url)

        return data
    }
}


let urls = [
    URL(string:"https://swift.org"),
    URL(string:"https://clojure.org"),
    URL(string:"https://apple.com")
].compactMap { $0 }

Task {
    for try await urlData in URLSequence(urls: urls) {
        if let rawHTML = String(data: urlData, encoding: .utf8) {
            print("rawHTML : \(rawHTML)")
        }
    }
}


// done!